1. Field of the Invention
The present invention relates to an image pickup apparatus such as a video camera and a digital camera, and to a viewfinder for the image pickup apparatus.
2. Description of Related Art
FIG. 26 to FIGS. 29A and 29B illustrate the structural arrangement of a conventional image pickup apparatus. In these illustrations, reference numeral 5000 designates an exterior cover of the image pickup apparatus and reference numeral 5001 denotes an image pickup lens. Although not shown, there exists an image pickup element for converting the light incident through the image pickup lens 5001 into an electric signal. Further, reference numeral 5011 represents a recording section for recording data on a recording medium 5050 such as a magnetic tape, and reference numeral 5012 signifies a signal processing circuit board for processing a picked-up image signal or the like. Still further, reference numeral 5013 indicates a battery for supply power to drive the whole video camera, and reference numeral 5014 stands for a monitor such as an LCD.
As seen in these illustrations, in the conventional image pickup apparatus, its components protrude by dimensions Aj, Bj and Cj with respect to the body with a dimension of Dj. This irregular configuration makes the inconvenience in encasing it in a bag or the like. In addition, when carried, the irregular configuration causes unstable conditions, that is, deteriorates its portability.
FIG. 28B shows a state where a cover 5011a is opened to remove/load the recording medium 5050. As seen from this illustration, in the case of the conventional image pickup apparatus, the recording medium 5050 is required to be taken out or loaded from the below. For this reason, when a tripod or the like is set onto a bottom surface section of the conventional image pickup apparatus, difficulty is encountered to remove/load the recording medium 5050.
Furthermore, reference numeral 5009 represents the optical axis of the image pickup lens 5001, and reference numeral 5014a designates a display screen of the monitor 5014. Further, reference numeral 5019 denotes the center line of the display screen 5014a. Still further, reference numeral 5030 signifies the hand of a photographer. As shown in FIG. 29A, when viewed from the top surface side of the image pickup apparatus, the image pickup lens optical axis 5009 is largely shifted by a dimension Pj with respect to the center line 5019 of the display screen 5014a. For this reason, the parallax is high at photographing, and particularly, when photographing a subject close thereto, the photographing becomes hard to extremely impair the convenience in handling.
In addition, as shown in FIG. 29A, when the photographer holds the conventional image pickup apparatus, the right-hand thumb section of the photographer reaches the display screen 5014a, and hence, the display screen 5014 is hidden to be hard to see due to the existence of the right-hand thumb section of the photographer, or the display screen 5014 is made dirty because of the appearance of fingerprints of the photographer, so that a problem on operability exists. Further, if the photographer holds the image pickup apparatus while avoiding the covering of the display screen 5014a by his or her thumb section, his or her right hand becomes limited in holding the image pickup apparatus, so that the operability extremely deteriorates in holding the image pickup apparatus.
Meanwhile, recently, in the field of an image pickup apparatus such as a recorder-integrated video camera (which will be referred hereinafter to as a video camera), the size reduction and the high-quality function have rapidly been in progress, and the convenience in handling to the user has improved. For instance, there has been proposed video cameras which can take various photographing positions. As one of these video cameras, there is a video camera equipped with both a liquid crystal monitor with a dimension of approximately 2 to 4 inches which is visible from a remote position and an eyepiece-type viewfinder which has an optical system in the middle and which is used in a state where the eye of the photographer is brought close to the eyepiece window.
In the case of such a video camera, the use of the viewfinder is possible in accordance with the photographing posture. For example, when taking a picture at a low angle or at a high angle, or when being attached to a tripod, that is, in cases where the photographing is more easily feasible if the eye of the photographer is separated from the video camera, the photographing is made through the use of the liquid crystal monitor, and in cases where the video camera is held by the hand of the photographer and used at an eye level, the photographing is done through the eyepiece-type viewfinder.
However, the video camera thus constructed is required to be equipped with a drive circuit, a signal processing circuit, a backlight and others for each of a liquid crystal panel for displaying a monitored image and an eyepiece viewfinder liquid crystal display unit, with the result that the increase in cost is unavoidable. For eliminating this problem, there has been proposed a structure in which the liquid crystal monitor is used as both the viewfinder (eyepiece-type) and the monitor. This is achievable in such a manner that an eyepiece section (eyepiece lens section) is installed in a liquid crystal monitor whose dimension is approximately 2 to 4 inches. This structure will be described hereinbelow.
FIG. 31 illustratively shows the structure of such a viewfinder. In FIG. 31, a first mirror 920 is obliquely placed in an opposed relation to a screen 901a of a liquid crystal panel 901, and a second mirror 921 is located in its reflection optical path. In addition, a positive lens 922 is situated between the second mirror 921 and the eye 907 of the photographer. The positive lens 922 is disposed at a position not existing above the screen 901a. The first mirror 920, the second mirror 921 and the positive lens 922 constitute an eyepiece section. This eyepiece section is made to be detachable from the viewfinder.
In such a structure, when directly viewing from a remote position, the photographer detaches the eyepiece section and directly looks into the viewfinder by the eye 907 from a direction opposite to the screen 901a of the liquid crystal panel 901. On the other hand, in the case of using the viewfinder as an eyepiece type, the viewfinder is used in a state where the eyepiece section is attached thereto. The image displayed on the screen 901a of the liquid crystal 901 is reflected by the first mirror 920 toward the second mirror 921, so that the second reflection occurs by the second mirror 921 to lead the reflected image toward the positive lens 922. The positive lens 922 forms the image from the second mirror 921 on the retina of the eye 907 of the photographer. In this case, because the reflection takes place twice by the mirrors 920 and 921, the image on the screen 901a again returns to an erecting image which in turn, is viewed by the photographer.
In the case of the viewfinder having the above structure, its screen size is considerably large as compared with a common eyepiece-type viewfinder, the magnification of the positive lens 922 provides a significant factor. That is, if the positive lens 922 is set to a magnification equal to that of the common eyepiece-type viewfinder, since the screen size is large and the size of each of the picture elements (pixels) constituting the screen is also large, two problems occur, that is, the image expands not to fall within the field of view of the photographer and each of the picture elements becomes coarsely conspicuous.
Assuming that the size of the screen 901a takes 3 inches (in diagonal length), for setting to a proper angle of visibility, the magnification of the positive lens 922, when expressed in focal length, comes to approximately 110 to 180 mm equivalent to four or five times that of the common eyepiece-type viewfinder, and hence, setting to a considerable low magnification is necessary. If setting to this magnification, the problem that the coarseness of each picture element is conspicuous is simultaneously solvable. However, the distance from the screen 901a to the positive lens 922 for offering a proper diopter is unconditionally determined to be a value close to 90% of the focal length. Accordingly, in the case of this example, the image goes back and forth through the optical path of approximately 100 to 160 mm due to the first mirror 920 and the second mirror 921, and then, is led to the positive lens 922.
However, in the case of the above conventional viewfinder, it is required that the first mirror 920 be placed at a position not blocking the light beam advancing from the second mirror 921 to the positive lens 922 and the second mirror 921 be placed at a position not obstructing the light beam advancing from the liquid crystal panel 901 to the first mirror 920, the configuration of the whole eyepiece section increases in volume to considerably protrude toward above the liquid crystal panel 901.